One percent of people participating in trials of Stribild or cobicistat became infected with HCV during the trials, a rate the researchers call "a small but notable proportion" [1]. Nineteen of these 20 people with acute HCV infection maintained undetectable HIV RNA during trial follow-up. No one became infected with HBV in these trials, perhaps because tenofovir and emtricitabine are active against HBV.

People enrolled in antiretroviral trials often remain at risk for HBV or HCV infection through sex or injection drug use. Whether to treat acute HCV infection during a clinical trial remains a pressing question. To address that issue and to assess rates of HCV and HBV infection in people participating in Stribild and cobicistat trials, Gilead Sciences investigators conducted this analysis of three trials of Stribild (elvitegravir, cobicistat, tenofovir, and emtricitabine) and two trials of cobicistat-boosted atazanavir plus tenofovir/emtricitabine. The trials randomized 2250 people and follow-up during antiretroviral treatment lasted for a median 107.3 weeks. The investigators eliminated people who tested positive for HBV or HCV at screening from analyses of incident HBV or HCV.

No cases of new HBV infection were recorded during the trials. Twenty people (0.93%) became infected with HCV for an incidence of 5.1 cases per 1000 person-years. Sixteen of these 20 (80%) had alanine or aspartate aminotransferase levels more than 3 times the upper limit of normal at the onset of HCV infection.

The 20 people with acute HCV infection--all of them men who have sex with men--had a median age of 36 years (range 23 to 57). Fourteen lived in North America, 4 in Europe, and 2 in Australia. Eighteen men were white and 2 Asian. Median time to acute HCV infection ranged from 41 to 845 days (median 424).

Four men dropped out of their trial when they picked up HCV; 3 of these 4 had an HIV load below 50 copies at the last study visit on therapy, and 1 had a load of 675 copies. All 16 men who remained in the trials had an HIV load below 50 copies at the last study visit. Six men started pegylated interferon and ribavirin for HCV infection; all 6 maintained an HIV load below 50 copies when they started HCV therapy.

Five of these 6 men completed at least 12 weeks of interferon/ribavirin and all achieved sustained virologic response (HCV RNA below 20 IU/mL 11 to 26 weeks after completing therapy). The man who stopped interferon/ribavirin after 11 weeks had an HCV load of 7.52 x log10 IU/mL 24 weeks after the last dose.

Among the 10 men with acute HCV infection who did not begin HCV therapy, 9 had detectable HCV RNA approximately 24 weeks after reported acute HCV onset.

The Gilead team suggested that lack of incident HBV infection in these trials--even though HBV and HCV share risk factors--is "consistent with other studies that indicate HBV acquisition in unlikely during treatment with an emtricitabine/tenofovir-containing HIV antiretroviral regimen."

The researchers proposed that antiretroviral trial planners might consider periodic HCV screening in study participants. If people become infected with HCV during the trial, the Gilead team suggested therapy for acute HCV infection may be considered without stopping antiretroviral therapy.